WO2001007372A1

WO2001007372A1 - Production method and device for sheet glass, and liquid crystal device

Info

Publication number: WO2001007372A1
Application number: PCT/JP2000/004898
Authority: WO
Inventors: Hiroyuki Kariya
Original assignee: Nh Techno Glass Corporation
Priority date: 1999-07-22
Filing date: 2000-07-21
Publication date: 2001-02-01
Also published as: JP2001031435A; JP3586142B2; US6758064B1; TWI230144B; KR20020021671A; KR100468542B1

Abstract

When producing a liquid crystal glass substrate by a down-load method, distortion caused by a cooling temperature difference for sheet glass is reduced, and fine distortion caused when sheet glass produced by a down-load method is segmented into small-size pieces is minimized. When sheet glass (8) is produced by a down-load method, a temperature distribution is formed in a width direction of the sheet glass (8) by a heat treating means (9) used in a slow-cooling process after forming. This temperature distribution can offset a sheet glass (8) temperature distribution caused when the sheet thickness of the formed sheet glass (8) is larger at its periphery than at its surface.

Description

Description Glass plate manufacturing method, glass plate manufacturing apparatus, and liquid crystal device

The present invention relates to a method for manufacturing a glass plate for manufacturing a thin glass plate (sheet glass) such as a glass substrate for liquid crystal, an apparatus for manufacturing a glass plate, and a liquid crystal device. Background art

As a method for producing this kind of sheet glass, a float method, a down-drawing method, and the like are known. In particular, from the viewpoint of cost, production of a glass substrate for a liquid crystal does not require polishing after molding or the polishing amount. The downdraft method, which has a small number, is widely used.

As an example of the down-draw method, for example, a method described in Japanese Patent Application Laid-Open No. H10-291826 has been proposed. In the method described in this publication, molten glass is continuously supplied from a melting tank along a molding surface, and the glass on both sides is fused below a molding die, and then the peripheral portion of the glass is rolled. The glass plate is manufactured by pulling downward. The glass plate obtained by such a manufacturing method has excellent smoothness and flatness because both main surfaces are formed as free surfaces during molding, and the glass surface in contact with the mold is fused. It has the advantage that.

Generally, a glass plate having an outer dimension of lmxlm and a thickness of 0.7 mm obtained by such a manufacturing method, such as 550 x 650 mm or 600 x 720 mm, is used. It is cut out in a small size and used as a glass substrate for liquid crystal. As a glass substrate for liquid crystal, a glass substrate for TFT And a glass substrate for a color filter.

Among these glass substrates, a thin film transistor (TFT) is formed on a glass substrate in a glass substrate for TFT, and a color filter is formed on a glass substrate in a glass substrate for color filter. Liquid crystal devices are manufactured by sandwiching liquid crystal between these glass substrates with thin films. However, the glass sheet manufactured by the conventional down-draw method has a problem that a large distortion is generated in a width direction of the sheet glass (a direction orthogonal to a tensile direction). The cause of this distortion is the thickness distribution peculiar to the downdraw method. Sheet glass manufactured by the downdraw method has a greater thickness at the peripheral portion in the width direction than at the inner portion (hereinafter referred to as the surface portion). As a result, when the sheet glass is gradually cooled from a high temperature after molding, the surface portion cools faster than the peripheral portion, so that a compressive stress is generated in the peripheral portion and a tensile stress is generated in the surface portion. As a result, small distortion occurs in the width direction. Also, this distortion tends to have a distribution such that the peripheral portion is relatively large with respect to the surface portion.

When a sheet glass having such a strain distribution is cut into a size of a glass substrate for a display device, the strain distribution remains in a rearranged state, and causes slight deformation of the glass substrate.

If thin film patterns of thin film transistors (TFTs) and color filters are formed by photolithography on a glass substrate on which such minute deformation has occurred, the exposure will not be performed properly as much as photolithography, and as a result, There is a problem that the accuracy of the thin film pattern is reduced.

In addition, when a TFT glass substrate and a color filter glass substrate are combined in a pair, a small deformation of the glass substrate causes a misalignment of the alignment mark, thereby reducing the yield of the liquid crystal device. The problem described above also occurs. In particular, as the size of the glass substrate increases, the amount of deformation of the glass substrate also increases, and pattern displacement has become a serious problem.

The present invention has been conceived in view of the above problems, and has the following objects.

An object of the present invention is to suppress the occurrence of minute distortion or minute deformation in a downdraw method.

Another object of the present invention is to prevent a pattern formed by photolithography on the surface of a glass substrate for a display device from causing a positional shift.

Another object of the present invention is to prevent the occurrence of distortion when a sheet glass formed by a downdraw method is cut into a predetermined size.

Still another object of the present invention is to improve the yield in manufacturing a liquid crystal device. Disclosure of the invention

In view of the above, the present invention proposes a manufacturing method in which, in a down-draw method, in order to remove a distortion caused by a temperature difference in a width direction of the sheet glass, a distortion reduction process of the sheet glass is performed during the slow cooling of the sheet glass. is there.

(Structure 1) A method for manufacturing a glass sheet, wherein a molten glass is formed into a sheet by a down-draw method, and the obtained sheet glass is gradually cooled by a heat treatment means to manufacture a glass sheet.

A method for manufacturing a glass sheet, comprising: performing a strain reduction process for reducing distortion of a sheet glass caused by a temperature difference between a peripheral portion and a surface portion in a width direction of the sheet glass at the time of slow cooling. . As a glass material suitable for the downdraw method, a material having a liquidus temperature of 1200 or less is preferable, and a material having a liquidus temperature of 110 Ot or less is more preferable from the viewpoint of devitrification. The thickness of the sheet glass is preferably 0.5 to 1.0 mm.

Further, it is preferable to perform the distortion reduction treatment immediately after the molding.

(Structure 2) The method for manufacturing a glass sheet according to Structure 1, wherein the temperature difference occurs between a peripheral portion and a central portion of the surface portion.

(Structure 3) A structure characterized in that the sheet glass introduced by slow cooling has a temperature distribution in the width direction such that the temperature is lower at the surface than at the periphery. 3. The method for producing a glass plate according to 1 or 2.

(Structure 4) The method of manufacturing a glass sheet according to any one of Structures 1 to 3, wherein the distortion reduction processing is performed based on a strain distribution in the formed glass sheet measured in advance by an optical heterodyne method. Method.

Since the distortion solved by the present invention is micro-strain (deformation), the amount of birefringence is measured by the optical heterodyne method that can measure micro-strain (micro-deformation) with high accuracy, and distortion reduction processing is performed based on the measurement result. Is preferred. By measuring the strain using the optical heterodyne method, the temperature distribution in the width direction of the formed sheet glass can be easily grasped.

(Structure 5) The distortion reducing treatment is performed in a predetermined manner in the width direction of the sheet glass so that the temperature difference in the width direction of the formed sheet glass is reduced when the formed sheet glass is gradually cooled by the heat treatment means. 5. The method for producing a glass sheet according to any one of Configurations 1 to 4, wherein the method is a heat treatment for forming a temperature distribution.

The temperature range for gradually cooling the sheet glass is preferably in the range of 600 to 850 t. The method of reducing the temperature difference in the width direction of the sheet glass is as follows. The heat treatment is preferably performed by a heat treatment means having a temperature distribution that offsets the temperature distribution in the lath width direction.

Further, since this heat treatment is performed in the slow cooling step, the temperature distribution in the width direction of the sheet glass also changes with the slow cooling time. Therefore, it is preferable that the temperature distribution of the heat treatment means is also formed by changing the temperature distribution continuously or stepwise along the tensile direction according to the changing temperature distribution of the sheet glass.

(Constitution 6) The method for producing a glass sheet according to constitution 5, wherein the heat treatment is performed at least in a process of gradually cooling the sheet glass from a forming temperature to a vicinity of a strain point.

The heat treatment is preferably performed in the range of the sheet glass forming temperature to the take-out temperature below the strain point, but it is effective to perform the heat treatment in the process of gradually cooling the sheet glass to the vicinity of the strain point from the forming temperature. Preferably, the heat treatment is performed in the process of gradually cooling the sheet glass from a temperature lower than its molding temperature by 400 to 500 ° C. to near the strain point. When the temperature in the width direction of the sheet glass is substantially equalized in the vicinity of the strain point and slow cooling is performed in the vicinity of the strain point, it is preferable to maintain the uniformed temperature state and further cool down. .

A preferred range near the strain point is within 5 O: of the strain point soil.

(Composition 7) The heat treatment is a process of setting a temperature distribution in the width direction of the sheet glass formed by the heat treatment means for heating the sheet glass so as to reduce a temperature difference in the width direction of the sheet glass. 7. The method for producing a glass sheet according to configuration 5 or 6, wherein

When the temperature distribution is formed by the heat treatment means, the temperature distribution near the strain point is used as a reference, and the temperature distribution that relaxes the temperature distribution near the strain point is formed as the strain point, rather than forming abruptly near the strain point. It is preferable to form stepwise or continuously during the slow cooling process between the temperature.

(Arrangement 8) The distortion reduction processing is performed on the periphery of the sheet glass in the width direction. In response to the difference in heat shrinkage generated between the surface and the surface, the amount of extension of the periphery relative to the amount of extension of the surface is increased compared to the amount of extension of the surface, so that the distance from the surface to the periphery 4. The method for producing a glass sheet according to any one of Configurations 1 to 3, which is characterized in that distortion generated over a portion is reduced.

The distortion reduction process is preferably performed in the process of gradually cooling in a temperature range of 600 to 850.

(Configuration 9) maximum strain of the manufactured sheet glass manufacturing method of the glass sheet, characterized in that 0.5 at 0 7KgZmm ² below.

Further preferred maximum strain is 0. 04 k gZmm ² below.

(Structure 10) The method for producing a glass sheet according to any one of structures 1 to 9, wherein the glass plate is a glass substrate for a display device.

As the display device, the liquid crystal device is preferably, in a liquid crystal glass substrate, the expansion coefficient of ^{3 2~ 3 8 X 1 0 7} Z:, strain point 6 5 0 or more.

By mol% when shown with the composition, 3 1 0 ₂ 6 0-7 0%, 8 ₂ 0 ₃ 7-1 2%, eight teeth ₂ 〇 _3. 9 to 1 3%, Mg O is 1-8 %,. 3_Rei is 2-8%, 5 1 "0 0.5 to 5%, 8 & 〇 is from 0.5 to 5% of the glass is preferred. Furthermore, 3 10 ₂ 6 5 to 7 5% B ₂力₃ force 6 ~: 1%, _{2 2} 〇 ₃ is 8 ~ 15%, MgO is 3 ~ 15%, CaO is 0 ~ 8%, 3 1''〇 is 0 ~ 1%, BaO Is preferably 0-1%.

(Configuration 11) A forming section for forming the molten glass continuously supplied from the molten glass storage tower into a sheet shape,

Pulling means for pulling down the softened sheet glass formed by the forming section,

And a distortion reducing means for reducing distortion caused by a temperature difference generated from a peripheral portion to a surface portion in a width direction of the sheet glass. Glass plate manufacturing equipment.

(Structure 12) The strain reducing means is a heat treatment means for gradually cooling the formed sheet glass, and has a temperature distribution that reduces the temperature difference in the width direction of the formed sheet glass. The apparatus for manufacturing a glass sheet according to configuration 11, wherein the apparatus is a heat treatment means that is set in a width direction of the glass sheet.

The heat treatment means is preferably disposed on one or both sides of the sheet glass. Further, it is preferable that the heat treatment means is disposed near the surface of the sheet glass.

(Structure 13) The distortion reducing means comprises a heat treatment means for gradually cooling the formed sheet glass, and a temperature difference from the surface portion to the peripheral portion generated in the sheet glass gradually cooled by the heat treatment means. Correspondingly, means for controlling the amount of extension of the peripheral portion to be greater than the amount of extension of the surface portion is provided.

(Structure 14) A liquid crystal device comprising a pair of glass plates formed by the method for manufacturing a glass plate according to any one of Structures 1 to 10, wherein a liquid crystal is sandwiched between the pair of glass plates. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of a glass sheet manufacturing apparatus according to one embodiment of the present invention for manufacturing sheet glass from molten glass.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a side view of the pulling roller shown in FIG.

FIG. 4 is a strain distribution diagram of a glass sheet not subjected to a strain reduction process. FIG. 5 is a table showing the temperatures of the heater and the glass in the distortion reduction process.

FIG. 6 is a graph of FIG.

FIG. 7 is a diagram showing a strain distribution of a glass plate subjected to a strain reduction process. FIG. 8 is a diagram showing the relationship between the shift amount of the total pitch of the glass sheet after division and the distortion amount of the sheet glass before division.

1 ... Molten glass storage tank, 2 ... Molten glass, 3 ... Molded part, 4 ... Head, 5 ... Tension roller, 6 ... Tension roller, 7 ... Tension roller, 8 ~ sheet glass, 9 ... Heat treatment means, 10 ... Annealing furnace. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of an apparatus for manufacturing a glass sheet according to one embodiment of the present invention for manufacturing sheet glass from molten glass, FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. Fig. 1 is a side view of the pulling roller, Fig. 4 is a strain distribution diagram of a glass plate that is not subjected to the strain reduction process, and Fig. 5 is the temperature of the heat (heat treatment means) and the sheet glass in the strain reduction process. Fig. 6 is a graph of Fig. 5; Fig. 7 is a graph showing the strain distribution of the glass plate that has been subjected to the strain reduction process; Fig. 8 is the total of the glass plate after cutting. FIG. 6 is a diagram showing the relationship between the pitch shift amount and the amount of distortion of the sheet glass before cutting.

(Glass plate manufacturing equipment)

First, a manufacturing apparatus for carrying out the method for manufacturing a glass sheet according to one embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG.

As shown in FIG. 1, the apparatus for manufacturing a glass sheet according to one embodiment of the present invention is generally constituted by a molten glass storage tank 1 and a lehr 10.

The molten glass storage tank 1 has a storage section 1a having an opening, and stores the molten glass 2 obtained by melting the glass raw material at a predetermined temperature in the storage section 1a. A molded part 3 is formed at the lower end of the storage part 1a. The molding 3 has a slit-shaped opening 3 a extending in the width direction of the sheet glass 8. The molded part 3 is made of a refractory brick whose surface is coated with platinum. Has been established.

Then, the molten glass can be formed into a sheet-like glass 8 by flowing the molten glass 2 through the opening 3a. The sheet glass 8 that has passed through the forming section 3 is gradually cooled by the heater 4 in order to prevent the peripheral portion from shrinking toward the surface portion due to rapid cooling.

The annealing furnace 10 is for gradually cooling the sheet-shaped glass 8, has a hollow inside, and heat-treats the sheet glass 8 while pulling the periphery of the sheet glass 8 downward with pulling rollers 5 to 7. Prevents rapid cooling of the sheet glass 8 and gradually cools it.

The pulling rollers 5 to 7 are arranged at a predetermined distance along the pulling direction of the sheet glass 8. In the vicinity of the main surface of the sheet glass 8, a heat treatment means 9 is arranged at a predetermined distance from and spaced from the main surface.

The pulling rollers 5 to 7 pull the sheet glass 8 downward across the peripheral portions 8 a and 8 b of the sheet glass 8. As shown in FIG. 2, the pulling rollers 5a, 6a, and 7a cooperate with the pulling rollers 5c, 6c, and 7c located on the back side of the sheet glass 8 to pull the sheet glass 8 together. It is pulling down. Although the right pulling rollers 5 b, 6 b, and 7 b shown in FIG. 1 are not shown, a pulling roller that pulls together is provided on the back side of the sheet glass 8.

The pulling rollers 5 to 7 arranged along the pulling direction of the sheet glass 8 are arranged such that adjacent rollers are offset by a predetermined amount in the thickness direction of the sheet glass 8. Thereby, the stroke of the peripheral portion is longer than that of the surface portion of the sheet glass 8. For example, the rollers (5a, 5c) (6a, 6c) (7a, 7c) located on the left side of FIG. 1 are rollers (6a, 6c) as shown in FIG. Are arranged so as to be deviated by α from the position of the rollers (5a, 5c) (7a, 7c). Roller shown in Fig. 1 5b, 6b and 7b are not shown, but have the same arrangement. The heat treatment means 9 for slow cooling can form a predetermined temperature distribution in the width direction of the sheet glass 8 and in the pulling direction so as to suppress generation of distortion. For this purpose, the heat treatment means 9 has a plurality of heaters arranged in the width direction (horizontal direction) and the pulling direction (vertical direction) of the sheet glass 8. The figure shows a case where eight heaters are arranged in the width direction of the sheet glass 8 as a representative. Although not shown in the drawing, for example, 10 heaters are arranged in the direction in which the sheet glass 8 is pulled. Each heater can control the temperature individually. The reason why a plurality of heaters are arranged in the width direction of the sheet glass 8 is to form a predetermined temperature distribution in the same direction that can reduce distortion in the same direction. The reason why a plurality of heaters are provided in the stretching direction of the sheet glass 8 is to form a predetermined temperature distribution in the same direction so that rapid cooling can be prevented and slow cooling can be performed. The quenching is prevented in order to prevent the sheet glass 8 from being damaged during the pulling process. In particular, if a sudden temperature change is applied to the sheet glass 8 in a temperature range of 600 to 700 ° C., the sheet glass 8 is easily broken by buckling deformation.

(Glass plate manufacturing method)

A method of manufacturing a glass plate using the above-described apparatus will be described below with reference to an example of manufacturing a glass substrate for liquid crystal.

First, preparations for distortion reduction processing are performed. First, the amount of distortion of the sheet glass 8 produced without performing the distortion reduction treatment is measured by an optical heterodyne method. The measurement sample is a glass plate cut out from the sheet glass 8 into a size of 65500 mm in width and 550 mm in depth. Fig. 4 shows the measurement results. As shown in the figure, the amount of distortion of the sheet glass 8 has a distribution that gradually increases from the center of the display portion to the peripheral portion. The strain is such that the folding amount Re is 4.1 nm (strain: 0.12 kg / mm ² ).

The scale in the figure indicates the length (mm). The center of each circle on the glass plate is the measurement point, and the size of the circle represents the magnitude of the distortion. Although not shown, f a s t a x i s, which indicates the direction of the distortion, faces the center of the lower end of the glass plate.

Next, data showing the correlation between the strain distribution measured in this way and the position adjustment amounts of the tension rollers 5 to 7 and the correlation between the strain distribution and the temperature distribution in the width direction of the heat treatment means 9 are shown. Collect data individually.

Based on this data, the amount of deviation of the tension rollers 5 to 7 that can reduce the occurrence of distortion and the temperature distribution in the width direction of the sheet glass 8 set by the heat treatment unit 9 are determined.

With such preparation, the sheet glass 8 is manufactured from the molten glass.

First, a raw material for aluminosilicate glass is melted in a melting tank (not shown) at a melting temperature of 1550 to 16500C, and then clarified and homogenized to obtain a molten glass. Then, the molten glass is transferred from the melting tank to the storage section 1a.

The raw materials of the aluminosilicate glass used were prepared to have the following glass composition.

S i 〇 _₂ 6 5%, B ₂ 〇 _{_{3 1 1%, AL 2 0}} 3 1 2%, Mg 01 2%,

C a〇 5%, S r O 2.4%, B a O 1.6%

The properties of this glass are as follows.

Strain point: 650 t: Photoelastic constant: 33 nm cm / kgf / cm ² Next, the molten glass 2 stored in the storage section 1 a is cut by the opening 3 a of the forming section 3. Formed into glass 8. The molding temperature at this time is 1 1 5 0 It is set to ~ 1250.

Then, the sheet glass 8 thus formed is gradually cooled while suppressing generation of distortion by the distortion reducing means.

Hereinafter, these distortion reduction processes will be described.

Two methods were used to reduce the strain: a method of controlling the amount of elongation of the sheet glass 8 due to the difference in heat shrinkage (method 1), and a method of forming a temperature distribution in the annealing step and heat-treating (method 2).

(Method 1: Deflection of pulling rollers 5-7)

When the sheet glass 8 is pulled downward by the pulling rollers 5 to 7, one of the adjacent rollers (the roller 6) is displaced by α, so that the peripheral portion of the sheet glass 8 is higher than the surface portion. It is greatly pulled. Thereby, a part of the distortion caused by the difference in thickness between the peripheral portion and the surface portion can be eliminated. This is due to the following effects.

At a predetermined interval in the feeding direction of the sheet glass 8, the amount of heat shrinkage between the surface portion and the peripheral portion is larger at the surface portion and smaller at the peripheral portion. Therefore, when the peripheral portion and the surface portion are pulled evenly, distortion occurs. Therefore, if the stroke of the peripheral part where the contraction is relatively small is made longer than that of the surface part, the stroke between the surface part and the peripheral part can be secured according to the difference in heat shrinkage. Can be suppressed.

(Method 2: Heat treatment by forming temperature distribution in slow cooling step)

As described above, the heat treatment means 9 of this embodiment has a plurality of heaters in the width direction and the pulling direction of the sheet glass 8 respectively. The table shown in FIG. 5 shows the temperature (V) of each heater arranged in the width direction and the pulling direction of the sheet glass 8, and the temperature (in) of the sheet glass 8 corresponding to each heater. ing.

In the vertical column of the table, there are duplicates sequentially arranged in the pulling direction of the sheet glass 8. The temperature of the heater and the temperature of the sheet glass 8 corresponding to each heater are shown. Here, “atmosphere” indicates the temperature of each day, and “glass” indicates the temperature of the sheet glass 8.

As the temperature of each heater, for example, the temperature of the atmosphere at a position 20 mm away from the surface of the sheet glass 8 measured by a thermocouple is shown. The temperature of the sheet glass 8 is a value obtained by measuring the temperature of the sheet glass 8 with a radiation thermometer.

The table shows the temperatures of the four heaters and the temperature of the sheet glass 8 corresponding to each of the heaters arranged sequentially from the forming section 3. Hereinafter, these four heaters will be referred to as first, second, third, and fourth heaters in order from the forming section 3.

Here, “1 atmosphere” to “4 atmospheres” indicate the temperatures of the first to fourth heaters, respectively. Similarly, “1 glass” to “4 glass” indicate the temperatures of the sheet glass 8 at the portions corresponding to the first to fourth heaters, respectively.

`` L '' in the column next to the table indicates the heater arranged at the left end of the sheet glass 8 in the width direction, and `` C '' indicates the heater arranged near the center, “R” indicates a heater arranged at the right end.

FIG. 6 is a graph of the table of FIG.

As can be seen from FIGS. 5 and 6, the temperature of the heaters arranged in the width direction of the sheet glass 8 is higher than the temperature of the heater arranged around the sheet glass 8 at the surface. It is set so that the temperature of the heaters arranged in the room increases. Specifically, the temperature of the central heater C is set to be 13 to 45 higher than the temperature of the surrounding heaters (R, L). The temperature difference is set so as to gradually decrease from the first heat to the fourth heat.

On the other hand, the temperature of the sheet glass 8 The temperature at the center of the surface of the sheet glass 8 is set to be 28 higher than the temperature at the periphery. On the other hand, in the part corresponding to the third heat sink, the temperature difference between the central part and the peripheral part of the surface is set to 3 t :. Thus, in this portion, the temperature is equalized in the width direction of the sheet glass 8. Further, in the portion corresponding to the third heat, the temperature of the sheet glass 8 is controlled to 65 ° C. which is the temperature at the strain point. That is, it can be seen that the temperature of the sheet glass 8 is equalized in the width direction near the distortion point of the sheet glass 8.

The heater that plays an important role in this embodiment is the third heater that performs heat treatment near the strain point. The first heater and the second heater are provided in order to avoid a rapid temperature change caused by rapidly cooling the sheet glass 8 from the forming temperature (1200 C) to the strain point. The fourth heater is provided for gradually cooling the sheet glass 8 to a lower temperature while maintaining the temperature distribution equalized by the third heater. The fifth to tenth heaters (not shown) that follow the fourth heat, while maintaining the temperature distribution equalized by the third heat, similar to the fourth heat, The sheet glass 8 is taken out and gradually cooled to a temperature (150 to 18 or). That is, the heat is gradually applied to the sheet glass 8 so that these heaters are gradually cooled while preventing rapid cooling.

Then, the sheet glass 8 sent to the takeout position is cut at predetermined intervals in the pulling direction and carried out.

The thickness of the sheet glass 8 after the completion of the forming is 4 to 6 mm at the peripheral portions on both the left and right sides (area of 120 to 130 mm inward from the end), and is 0 at the surface located inside. 7 mm. As for the outer shape, the width is 106 mm and the depth is 110 mm. After this, the thickness is controlled The glass plate having an effective width of 800 mm and a depth of 110 mm was manufactured by removing the peripheral portion that was not formed. Here, the effective width is the width of a region having a uniform thickness.

Thereafter, the glass plate was sequentially polished and washed to complete the final product. The distortion of the glass plate thus manufactured was measured by the optical heterodyne method. As a result, the maximum birefringence amount Re was 0.77 (maximum strain: 0.04 kg / mm ² ). FIG. 7 shows the measurement results of the stress distribution in this example. As shown in the figure, not only the suppression of the maximum value of the distortion, but also the distribution of the distortion is almost equalized.

In addition, comparing the glass plate of this example with the conventional glass plate manufactured without performing the distortion reduction processing shown in FIG. 4, the uniformity of the distortion and the reduction of the amount of distortion are not significant. It turns out that the glass plate of an Example is excellent. Further, in the present example, the breakage of the sheet glass 8 caused by the distortion during the slow cooling process was prevented, so that the yield was improved by 10%.

(Manufacture of liquid crystal devices)

A liquid crystal device was manufactured from the glass plate manufactured according to the above-described embodiment. Specifically, two glass plates of 42.times.275 mm were cut out of a full-size glass plate of 550.times.650 mm. The total 'pitch' shift amount of the cut glass plate was 0.40 / m. It is preferable that the total pitch shift is 1 m or less.

If the relationship between the total pitch shift amount and the distortion of the full-size (the size of the glass plate before cutting) glass plate is determined in advance, the distortion amount of the full-size glass plate can be calculated. By controlling the shift, it is possible to manage the shift amount of the total pitch of the glass plate used for the actual display device. FIG. 8 is a graph showing the correlation between the two. In the figure, the vertical axis shows the total pitch generated in the glass plate obtained by the division. The horizontal axis indicates the birefringence (nm) of the full-size glass plate before cutting.

A glass substrate for a color filter and a glass substrate for TFT were manufactured from the glass plate of this example in which the distortion was suppressed in this manner. Then, a liquid crystal device was manufactured by aligning the alignment marks on each glass substrate. In this case, since the glass plate with reduced distortion of this example was used, a liquid crystal device could be manufactured with a high yield.

The present invention can be applied to a down-draw method other than the down-draw method of the above-described embodiment. For example, the present invention can also be applied to the conventional downdraw method described in the section of Background Art.

Further, in the above-described embodiment, a case has been described in which two types of distortion reduction processing are used as the distortion reduction processing. However, in the present invention, only one of the distortion reduction processings may be used.

Further, in the above-described embodiment, a plurality of heaters are arranged in the width direction of the sheet glass 8 as the heat treatment means, and the temperature of each heater is individually controlled, so that a predetermined temperature distribution is obtained in the same direction. The case where the heat treatment means for setting is used has been described. However, the present invention has a single heater that uniformly generates heat as a whole. For example, by appropriately arranging a heat insulating material on the surface of the heater, a predetermined temperature distribution can be obtained in the width direction of the sheet glass 8. A heat treatment means for setting the temperature may be used.

The present invention can also be applied to the manufacture of glass substrates used in display devices other than liquid crystal devices and glass substrates used in other electronic products (for example, glass substrates for information recording media). Industrial applicability

According to the present invention, sheet glass in which distortion is suppressed is applied to a down draw method. Therefore, it can be manufactured. In particular, distortion in the width direction of the sheet glass can be suppressed. For this reason, distortion of the glass plate cut out from the sheet glass can be suppressed.

Therefore, when a fine pattern is formed on a glass plate manufactured by the present invention by a photolithography method or the like, a positional shift of the pattern can be suppressed.

Further, according to the present invention, when sheet glass is produced by the down-draw method, since the occurrence of thermal distortion is suppressed, when the sheet-shaped glass is gradually cooled while being pulled, the sheet-shaped glass is Damage can be prevented. For this reason, the production yield can be improved.

Further, according to the glass substrate for display manufactured by the present invention, the yield in manufacturing the display device can be improved.

Claims

The scope of the claims

1. In a glass sheet manufacturing method, a molten glass is formed into a sheet shape by a down draw method, and the obtained sheet glass is gradually cooled by a heat treatment means to manufacture a glass sheet.

Manufacturing a glass sheet, characterized in that a distortion reduction treatment for reducing distortion of the sheet glass caused by a temperature difference between a peripheral portion and a surface portion in the width direction of the sheet glass is performed at the time of slow cooling. Method.

2. The method for producing a glass sheet according to claim 1, wherein the temperature difference occurs between the peripheral portion and a central portion of the surface portion.

3. The sheet glass introduced slowly is a glass having a temperature distribution in a width direction thereof such that a surface portion has a lower temperature than a peripheral portion. 3. The method for producing a glass sheet according to claim 1 or 2.

4. The method according to claim 1, wherein the distortion reduction processing is performed based on a distortion distribution in the glass plate after forming, which is measured in advance by an optical heterodyne method. 3. The method for producing a glass plate according to 1.

5. The distortion reducing treatment is performed so that, when the formed sheet glass is gradually cooled by the heat treatment means, a temperature difference in the width direction of the formed sheet glass is reduced. The method for producing a glass sheet according to any one of claims 1 to 4, wherein the heat treatment is a heat treatment for forming a predetermined temperature distribution.

6. The method for manufacturing a glass sheet according to claim 5, wherein the heat treatment is performed at least in a process of gradually cooling the sheet glass from a forming temperature to a vicinity of a strain point.

7. The heat treatment is performed by a heat treatment means for heating the sheet glass. 9. A process for setting a temperature distribution in a width direction of the sheet glass to be formed so as to reduce a temperature difference in a width direction of the sheet glass. Item 7. The method for producing a glass sheet according to Item 6 or 6.

δ 8. The distortion reduction processing includes: elongating the peripheral portion with respect to the surface portion in accordance with a heat shrinkage difference generated between the peripheral portion and the surface portion in the width direction of the sheet glass. 4. The method according to claim 1, wherein the strain generated from the surface portion to the peripheral portion is reduced by increasing the extension amount of the surface portion. A method for producing a glass plate according to any one of the above.

9. The method for manufacturing a glass sheet according to any one of claims 1 to 8, wherein a maximum distortion of the manufactured sheet glass is 0.07 Kg / mm ² or less. .

10. The method for manufacturing a glass plate according to any one of claims 1 to 9, wherein the glass plate is a glass substrate for a display device.

1 1. A forming part for forming the molten glass continuously supplied from the molten glass storage tower into a sheet,

Pulling means for pulling the softened sheet glass formed by the forming section downward,

A glass sheet manufacturing apparatus, comprising: a distortion reducing unit configured to reduce distortion of the sheet glass caused by a temperature difference generated from a peripheral portion to a surface portion in a width direction of the sheet glass.

12. The strain reducing means is a heat treatment means for gradually cooling the formed sheet glass, and has a temperature distribution that reduces a widthwise temperature difference 5 in the formed sheet glass. The heat treatment means set in the width direction of the sheet glass, wherein the heat treatment means

1 3. The distortion reducing means is:

Heat treatment means for gradually cooling the formed sheet glass,

In accordance with a temperature difference between the surface portion and the peripheral portion generated in the sheet glass which is gradually cooled by the heat treatment means, the extension amount of the peripheral portion is set to be larger than the extension amount of the surface portion. The means to control

14. The method for producing a glass sheet according to claim 11, wherein the glass sheet is formed by the method for producing a glass sheet according to any one of claims 1 to 10. A liquid crystal device characterized by sandwiching liquid crystal between a pair of glass plates.